2019    2018    2017    2016    2015    2014    2013    2012    2011    2010    2009    2008 2010.3.4    2010　Annual Report (3)  H. Yamamoto, H. Cui, M. Nomura, J. Lieffrig 2010.2.25    Literature survey 2010.2.12    2010　Annual Report (2)  Y. Oshima, Y. Kawasugi, J. Ueno 2010.2.4    2010　Annual Report(1)  N. Tajima, A. Tajima, N. Takubo 2010.1.21    "Superconductivity in diamond" National Institute for Materials Science (NIMS), Nano Frontier Materials Group (NFM) Prof. Y. Takano Superconducting boron-doped diamond films were successfully synthesized using the microwave plasma assisted chemical vapor deposition (CVD) method. For an increasing of boron concentration, the metal-insulator transition took place at NB = 3e20 cm-3, and achieved superconductivity around 11.4 K for Tc onset and 8.4 K for zero resistivity in (111) films at NB = 8e21 cm-3. On the other hand, the superconductivity in (100) films was strongly suppressed even at the same boron concentration. To analyze the difference of superconductivity between (111) and (100) films, we performed NMR measurements, and found that there were single and pair boron and the (111) film contained single boron much larger than that of (100) film. The band calculation suggest only single boron can contribute to the carrier doping into diamond band. For improvement of superconductivity in boron-doped diamond, the increasing of single born is essential. In my presentation, I will also mention about the electrical band structures analyzed by ARPES and XAS. Using the characteristics of the superconductivity, which occur in the doped-semiconductor, we are currently developing new devices such as a Josephson junction composed of only single crystal diamond. 2010.1.14    "X-ray Irradiation-Induced Carrier Doping Effects and Optical Probe in the Organic Dimer Mott Insulator"  J. Ueno Carrier doping effect is induced in X-ray irradiation to the organic dimer-mott insulators κ-(ET)2X with X = Cu[N(CN)2]Cl and Cu2(CN)3.For κ-(ET)2Cu[N(CN)2]Cl, a large decrease of the resistivity at 300K and the metal like temperature dependence down to about 50K have observed.The irradiation-induced defects result in the effective doping of carriers. From investigation of the infrared optical spectra of κ-(ET)2Cu[N(CN)2]Cl, they observed that the irradiation caused a large spectral weight transfer from the midinfrared region to a Drude part in low-energy region.the increase of the Dorude part indicates a carrier doping into the mott insulator due to irradiation defects. 2009.12.24    Literature survey 2009.12.21    "Disoreder induced superconductor-insulator transition in κ-(BEDT-TTF)2Cu[N(CN)2]Br irradiated by X-ray"  T. Sasaki  /  Low Temperature Physics division, Institute for Materials Research, Tohoku University   Associate Professor, Organic charge-transfer salts based on a donor molecule bis(ethylenedithio)-tetrathiafulvalene (abbreviated BEDT-TTF) have been recognized as one of highly correlated electron systems. Among them, κ-(BEDT-TTF)2X with X = Cu(NCS)2, Cu[N(CN)2]Y (Y = Br and Cl), etc. has attracted considerable attention as a bandwidth-controlled Mott transition system because of its strong dimer structure consisting of two donor molecules, which effectively makes the conduction band a half-filling band. Recently, a study was conducted on the effect of X-ray irradiation-induced carrier doping on the dc conductivity and optical conductivity of an organic dimer-Mott insulator κ-(BEDT-TTF)2Cu[N(CN)2]Cl. We observed a large reduction of the dc resistivity and a large enhancement of the Drude part in a low-energy region of the optical conductivity. These results indicate a carrier doping into the Mott insulator. The carrier doping introduced by the X-ray irradiation also causes a disorder effect which will induce a carrier localization by random potentials as Anderson-type insulators. It is interesting to investigate the random potential effect in the strongly correlated electron systems. We measured the temperature dependence of the resistivity in the X-ray irradiated organic superconductor κ-(BEDT-TTF)2Cu[N(CN)2]Br which is located nearby the Mott transition. With increasing the irradiation dose by the X-ray irradiation using the tungsten tube with 40 kV, 20 mA, the superconducting transition temperature decreases accompanying the increase of the residual resistivity as has been observed in κ-(BEDT-TTF)2Cu(NCS)2. An insulating behavior, however, appears at low temperatures in the resistivity of the samples with longer irradiation times. The observed correlated metal (superconductor) -insulator transition is induced by the random potential effect, which may be qualitatively different from the Mott transition. We will discuss the random potential effect near the Mott transition in the organic dimer-Mott system on the basis of the experimental results of the dc conductivity and the optical conductivity spectra. 2009.12.1    "Spin excitations of Dirac particles in α-(ET)2I3"  Y. Shimizu  /  Institute for Advanced Research, Nagoya University  Associate Professor Static and dynamic spin susceptibilities of the Dirac particle are investigated by 13C NMR measurements of the quasi-two-dimensional organic conductor (ET)2I3 under hydrostatic pressure. The 13C Knight shift decreases abruptly below 80 K, which faster than T-linear expected in the gapless state, without a diamagnetic shift. The T4 power-law decay in the nuclear spin-lattice relaxation rate 1/T1 also suggests gapped spin excitations. No magnetic field and angular dependences were observed in 1/T1, which is inconsistent with the low-energy spin excitations at the zero-mode Ladau level with the Zeeman splitting. 2009.11.26    "Self-assembled nanostructures"  Julien LIEFFRIG There is currently intense interest in the development of molecular electronic devices, and particularly the facile construction of effective molecular wires or conductive architectures. These architectures are synthetic nanometer-sized materials that are capable of directional, long-range electron transport. Chemically programmed self-assembly has been recognized as a powerful approach to the fabrication of these electroactive nanostructures. 2009.11.19    "Magnetoconductivity studies of dicyano(phthalocyaninato) iron conductor "  M. Kimata  /  Exploratory Nanomaterials Research Laboratory, NIMS   Nano-quantum Transport Group Interplay between magnetism and conductivity is one of the central issue of the present condensed matter physics. In this seminar, I would like to talk about the giant response to magnetic and electric fields observed in the dicyano Fe-Phthalocyanine conductor TPP[Fe(Pc) (CN)2]2 (magnetoresistance (MR) and non-linear current-voltage (I-V) characteristics). The change of the MR amounts to four orders of magnitude or over below 10K. This MR effect is associated with the magnetic torque anomaly at 15T, suggesting the existence of some magnetic field induced transition. The detailed analysis of the I-V characteristics show that the electric flux distribution, i.e., the dimensionality of the Coulomb interaction between carriers, also changes at 15T. 2009.11.12    "Mysterious Paramagnetic States of Fe Spin in Antiferromagnetic Insulator > of λ(BETS)2FeCl4 System"  H. Akiba / Department of Physics, Faculty of Science, Toho University  /  Doctor Course 1 In this study, we have investigated a quasi-two-dimensional organic conductor, λ(BETS)2FeCl4, that exhibits a phase transition from a paramagnetic metal to an antiferromagnetic (AF) insulator at a critical temperature (TMI = 8.3 K). To investigate the mechanism of a notable phase transition, we studied the thermal properties of the conductor for temperatures down to 0.2 K at zero magnetic field. We observed that the specific heat of the conductor showed a sharp peak at TMI and a Schottky-type hump. The temperature dependence of the excess specific heat clarifies that π and 3d spins do not cooperatively form an AF order at TMI. We concluded that a 3d spin system keeps a paramagnetic state even at the lowest studied temperature. 2009.11.05    "Organic spin-valve device"  Y.　Kawasugi Spin dependent transport has attracted much attentions due to interesting phenomena like giant-magnetoresistance (GMR) effect.I will introduce spin-valve devices using organic materials such as　Alq3, in which the spin diffusion length is much longer than that of conventional inorganic insulators. 2009.10.29    "Proposed Chiral Dithiolene Complexes as Molecular Conductors"  M.　Nomura Many chiral TTF derivatives involving their enantiomers, racemic mixtures and diastereomers have been synthesized so far, and their physical properties have been developed as well. Among them, one important observation in those studies is that all conductivities are different between those chiral isomers. Since chiral dithiolene complexes have been rarely reported, here I would like to propose some synthetic strategies for new chiral dithiolene complexes which are probably useful for molecular conductors. 2009.10.22    "Photoinduced insulator to metal transition in BEDT-TTF salts using pump-probe spectroscopy"  N. Takubo In this seminar, I will review recent studies about photoinduced phase transition in BEDT-TTF salts using pump-probe spectroscopy, which have been reported by Iwai group. Transient photoinduced insulator to metal transitions by different mechanism in α-(BEDT-TTF)2I3, θ-(BEDT-TTF)2RbZn(SCN)4 and κ-(BEDT-TTF)2Cu[N(CN)2]Br have been observed. 2009.10.15    Literature survey 2009.10.6    "Development of new porous molecular dielectric materials"  Cui　Hengbo Metal-Organic Framework (MOF) porous crystals containing guest　molecules provide a unique opportunity for developing new molecular materials with functions that depend on the guest molecules and also for studying the fundamental physical properties of nanomolecular assemblies confined in confined spaces. In this seminar, I will mainly present two types of porous materials that exhibit ferroelectric and antiferroelectric properties. 2009.9.10    "Strategies towards chiral molecular conductors"  Dr. Narcis Avarvari Introduction of chirality into conducting systems is a topic of much current interest as it allows the preparation of multifunctional materials in which the chirality may modulate the structural disorder or expresses its influence through the electrical magneto-chiral anisotropy effect. The access to various chiral electroactive precursors for molecular conductors is therefore of paramount importance. For example, chirality can influence the structural disorder of crystalline TTF based materials, and hence their transport properties, such as we demonstrated within a couple of complete series of (±), (R) and (S) molecular conductors based on chiral TTF-Oxazolines (TTF-OX). Starting from these results, several new strategies to address the chiral information have been imagined and will be discussed during the lecture. 2009.9.8    "Halogen Bonding and Metal Ion Coordination in Supramoleular Complexes"  Prof. Kari Rissanen Predicting and designing non-covalently bound supramolecular complexes and assemblies is difficult because of the weakness of the interactions involved, most recent of these being the interaction between polarized iodine atoms and nucleophilic atoms (N, O, S) or anions (iodide, bromide, etc..), viz. the halogen bonding. Our research interest has been focused on the studies of weak non-covalent intermolecular, viz. supramolecular interactions as the driving force in self-assembly and molecular recognition, especially in the solid state by single crystal X-ray diffraction. The lecture will highlight some of our recent studies on halogen bonding and metal ion coordination in molecular self-assembly and molecular recognition in various systems. 2009.7.22    2009　Midterm report�B  H. Yamamoto, H. Cui, M. Nomura, J. Lieffrig 2009.7.15    2009　Midterm report�A  Y. Oshima, N. Takubo, Mohamad. M. Ahamad, J. Ueno 2009.7.8    2009　Midterm report�@  N. Tajima, A. Tajima, Y. Kawasugi 2009.7.1    "Non-contact transport measurement: Application to nano-scaled materials"  Y. Oshima Few weeks ago, Tajima-san has lead us to discover the deepness of resistivity. Here in this seminar, I will talk about the method for measuring the resistivity 'without contact', and its application to nano-scaled materials such as single-walled carbon nanotube, single-molecule magnet and nanowire. I will try to explain the pros and cons of this technique. 2009.6.24    Literature survey   2009.6.10    "Resistivity is deep"  N. Tajima Everyone can examine the resistivity of conductors easily. New system (physics) is often discovered from the examination of resistivity. Many physicists try to discuss the physics from the behavior of resistivity. But, some cases might be wrong. The bad electrodes often lack validity of resistivity. In this seminar, you will understand the importance of electrode. 2009.6.3    "Recent advances in Halogen bond"  H. M. Yamamoto Halogen bond has been known for a long time, but has not　attracting very high attention. Recently, however, several major　progresses related to the halogen bond have been made in theory,　material science, and biology. In this seminar, I will describe these　research topics and compare them with our own results in molecular　conductors. 2009.5.27    "High pressure transport study by using DAC(Diamond Anvil Cell)"  Cui Hengbo I will introduce my previous work during the period of IMS and NHMFL. I will mainly talk about high pressure transport studies on organic conductors by using diamond anvil cell (DAC). Also talk about recent results on the studies of single component material [Ni(ptdt)2], and inorganic material (Germanium) by using newly improved technique. If there is enough time, I will present the studies of new molecular porous dielectric materials. 2009.5.20    "Frustration and Valence Bond Formation in a Molecular Mott System"  R. Kato A possibility of a quantum spin liquid state and related phenomena in a two-dimensional molecular Mott system based on the Pd(dmit)2 (dmit = 1,3-dithiole-2-thione-4,5-dithiolate) molecule will be demonstrated. The Pd(dmit)2 molecule provides conducting anion radical salts with closed-shell monocations A common feature of these Pd(dmit)2 salts is a conducting anion layer with a quasi (isosceles) triangular lattice of the dimer unit [Pd(dmit)2]2-. The conduction band is half-filled and two-dimensional. At ambient pressure, all the Pd(dmit)2 salts behave as Mott insulators where one spin is localized on each dimer. Interdimer transfer integrals can be tuned by the choice of the cation, which provides a variety of electronic states. The EtMe3Sb salt has a nearly regular-triangular lattice. The temperature dependence of the magnetic susceptibility is described by the antiferromagnetic spin-1/2 Heisenberg model on the triangular lattice with an exchange interaction J=220-250 K. The 13C-NMR shows no indication of either spin ordering/freezing down to ca. 20 mK. Below about 1 K, the spin-lattice relaxation rate T1-1 curve starts to bend and is proportional to T2. On the other hand, the temperature dependence of the specific heat was found to include a linearly temperature-dependent term (the γ term) with γ=15~20 mJ K-2 mol-1. Preliminary thermal conductivity measurements indicate an increase of κ /T with lowering temperature. These results suggest that the spin frustration leads the EtMe3Sb salt into a spin liquid state. When the deviation from the regular triangular lattice is large, the antiferromagnetic long range order is dominant and the frustration is removed. On the other hand, in the system with a nearly regular triangular lattice, the spin liquid state appears to compete with the static valance bond formation. The Et2Me2Sb salt undergoes a first-order transition toward a charge separation state (2Dimer- → Dimer0 + Dimer2-) at 70 K. In the EtMe3P salt, a second-order transition from the frustrated paramagnetic state to the valence bond solid (VBS) state with a spin gap occurs at 25 K. The former is an "intra-dimer" valence bond formation, and the latter an "inter-dimer" one. The VBS state in the EtMe3P salt turns to a superconducting state under pressure. 2009.5.13    "Electron spin resonance study of charge carriers in organic field-effect　devices"  Prof. S. Kuroda ／Department of Applied Physics, Graduate School of Engineering, Nagoya University Organic field-effect transistors (FETs) of conjugated molecules and polymers, such as pentacene and regioregular poly(3-alkylthiophene)s (RR-P3ATs) attract much attention owing to their high mobilities ranging from 0.1~10 cm2V-1s-1. In this talk, recent electron spin resonance (ESR) studies of field-induced charge carriers at the insulator-semiconductor interface in those devices are discussed. The field-induced ESR (FI-ESR) provides microscopic information such as spin-charge relation and wave functions of carriers and the molecular orientations at the device interface, which crucially probes the electronic states of the active layers of FETs, typically one to a few monolayers thick. From these studies, spin crossover phenomena from polarons to spinless bipolarons (or plaron pairs) in RR-P3AT and the band-like transport in pentacene have been demonstrated. 2009.4.27    "Thermodynamic Properties of Two-Dimensional Quantum Spin Liquid in Molecular Crystals"  S.Yamashita／Mr. Satoshi Yamashita (D2) Department of Chemistry, Osaka University I will talk about peculiar thermodynamic features of spin-liquid state with stoichiometric composition. By low-temperature heat capacity measurements, a distinct T-linear contribution of Cp was detected in the two salts below 2 K. The existence of T-linear contribution has been considered as a strong evidence for the realization of RVB state. Furthermore, I have observed a curiously broadened hump structure around 3 K for EtMe3Sb[Pd(dmit)2]2 and 5.5 K for κ-(BEDT-TTF)2Cu2(CN)3.Probably these anomalies are related to the crossover between the spin-liquid ground state with strong quantum characters and the classical Heisenberg-state in the 2D triangular structure. The observation of condensation temperatures of the quantum spin liquids can give a new issue for physical chemistry of correlated spin systems. The structural difference of the two salts will be discussed in relation to the difference of the condensation temperatures from the thermodynamic standpoints.